It's supposed to last 12 seconds (=4 rounds), dealing 1 point damage to each attribute every second.

Instead, it lasts 72 seconds (=24 rounds), dealing 1 point attribute damage every 6 seconds (=every second round). So basically it's an effective saving throw decrease of 1 point at most, given the enemy has an even number Con/Dex/Wis, unless you are willing to wait for over a minute until the spell kicks in fully.

Damn it! I knew there was something wrong! I was casting it on enemies in both Kotors and it's always just one point saving throw decrease. Now I understand why!

The spell effect in Kotor 1 is applied permanently (1000 seconds to be precise). This doesn't matter however, since the spell gets its duration from poison.2da, NOT from the spell script. Seems Obsidian didn't get this, cause they added the following to their k_inc_force.nss:

Obsidian, it doesn't matter what the script says, it's the "duration" column in poison.2da that defines the effect duration! That's where EffectPoison gets its duration from! And that is exactly the problem - poison.2da file has wrong values!:

In Kotor 2, several enemies on Korriban have a saving throw DC of 60-100. Plague is supposed to be irresistable (DC =100), meaning it's supposed to have a success chance of 100 per cent. Yet the Raven phantom on Korriban has a Fortitude saving throw of 100, which ironically means the spell has a success chance of 0, yes, ZERO per cent! Why? Because even if Raven gets a roll of 1, it's still 100 + 1=101 vs. Plague DC 100! Saving throw successful, thank you very much Obsidian!

Same goes for Sion and several Sith Assassins on Korriban, if they get a roll of 20, they shoot right over 100 saving throw DC, saving themselves from Plague! Plague needs a DC of 121 to have 100 per cent of success: